1. Field of the Invention
The present invention relates to a communication system in which voice is reproduced on a real time basis in two or more terminal equipments, server equipment that is used in such a communication system, and terminal equipment that is used in such a communication system.
2. Description of the Related Art
Recently, IP (Internet Protocol) telephones, which talk over the telephone using terminal equipment connected with an IP (Internet Protocol) net, through the IP net, have come into wide use rapidly. Particularly, technologies referred to as PoC (Push-to-Talk over Cellular) that performs a broadcast voice call (session), and PoC/W (Push-to-Talk over Cellular/Wireless), attract attention by using the terminal equipment of the IP telephone like the transceiver among two or more users (for example, refer to Japanese Patent Publication TokuKai. 2006-135511 and Japanese Patent Publication TokuKai. 2006-180143). Hereafter, it is called PoC especially distinguishing neither PoC nor PoC/W.
According to PoC, a communication system, which comprises two or more terminal equipments and a predetermined server equipment, is constructed in such a way that the server equipment establishes a communication line between terminal equipments each two or more users that participate in one session. According to the communication system, audio data transmitted from arbitrary terminal equipment is transferred by the server equipment to other terminal equipment, so that the terminal equipment of the destination reproduces the voice represented by the audio data on a real time basis. Thus, the session among two or more users is possible.
Transmission of audio data in the communication system is permitted when the terminal equipment obtains the right (speaker right) of transmission of audio data. A switch special to demand this speaker right from the server equipment has been often installed in the terminal equipment of PoC. When the user depresses the switch, the server equipment gives the speaker right to the user's terminal equipment. When the user speaks while pushing the switch, the voice data representative of the speaking voice are transmitted from the server equipment to other terminal equipments on a broadcast basis. At that time, the effect that the speaker right is being acquired by other terminal equipment now is notified to other terminal equipments. When the user of the terminal equipment having the speaker right, that is, the speaker terminates the speech and releases the switch, the speaker right is restored to the server equipment, and the acquisition of the speaker right with other terminal equipments becomes possible. Thus, according to PoC, acquisition and restoration of the speaker right are repeated between the terminal equipments in the communication system, so that voice interaction is carried out between two or more users.
According to PoC as mentioned above, in the event that it is desired to pass on certain information to two or more users, it is possible to pass on once speech to two or more users on a broadcast basis. This feature makes it possible to reduce cost and time for talking to two or more users. Moreover, in the event that the other party, who is a person of interest to speak, is as much as one person, contents of the speech are transmitted to two or more users on a broadcast basis. This feature makes it possible to share among two or more users contents of speech and the fact recognition that the contents were passed on to the one other party.
By the way, there is a case where, in talking by using PoC only, it is desired to talk only to some of users who are participating in the session.
For example, it is considered that a communication system using PoC is applied to a so-called taxi radio system for performing a radio communication between a management center and two or more taxies in a taxi company. In this case, there is established a session in which the management center and two or more taxies participate. While there is a need that an instruction from the a management center is transmitted to all the taxies, it is desirable that speech contents from individual taxies to the management center are transmitted to only the management center, since there is a possibility that the speech contents from individual taxies to the management center include client information and the like. Moreover, for example, it is considered that a communication system using PoC is applied to a session among a construction manager and two or more workers in a construction site. In this case, there is established a session in which the construction manager and two or more workers participate. While there is a need that an instruction from the construction manager is transmitted to all the workers, there is no need for the construction manager to receive speech contents telling work situation detailed among workers each other, and it is desirable that such speech contents are transmitted to only the workers. Still moreover, for example, it is considered that a communication system using PoC is applied to a general session among two or more users. In this case, assuming that some users wish to have a confidential talk with a part of the users while all talking, it is desirable that speech contents of the user who talks in whispers are transmitted to only the party of the secret story.
However, it is principally impossible for the conventional communication system using PoC to talk over with only some uses of the users who participates in a session. To talk over the telephone only to some users with the conventional communication system, a new session that consists only of the speaker and some the users is needed besides a present session. For example, according to the above-mentioned taxi radio system, there is needed a session in which two parties of individual taxi and the management center participate, in addition to the session in which all taxies and the management center participate. The later session is needed for each taxi. Moreover, according to the example of the session of the construction site, there is needed a session consisting of only the workers, in addition to the session in which all workers and the construction manager participate. Still moreover, according to the example of the session of the confidential speech, there is needed a session consisting of only the users who wish to have a confidential talk, in addition to the session in which all users participate. When the users who participate in a confidential talk changes, a new session is needed in every case.
It not only increases the resource consumed on the network used to communicate but also obliges the system to establish additional two or more sessions to hold two or more sessions like this. Thus, this involves a problem that complex management of these two or more sessions is needed.
In the above, though it explained the problem when talking by PoC only to some users of users who are participating in the session among users who participate in the session enumerating the communication system using PoC as an example, such a problem is a problem that can be caused by common to the communication system that performs a broadcast data communication between two or more terminal equipments.